Impact tool



Aug. 19, 192 1,505,493

E. w. ROBERTS IMPACT TOOL I Filed Aug. 13. 1920 2 Sheets-Sheet l Aug. 19, 192?}.

- E. w. ROBERTS IMPACT TOOL 2 Sheets-Shoot 2 Filed Aug. 13

Patented Au 19,1924. STATE EDMUND WILLSON 1,505, PATENT ounce...

ROBERTS,.OF CINCINNATI, OHIO, ASSIGNOR OF ONE-HALF TO 0. S.

SOMERVELL,.OF RIVEBTON, NEW JERSEY.

IMPACT TOOL.

Application'filed August 13, 1920. Serial No. 403,194.

To all whom it may concern Be it known that I, EDMUND WILLsoN ROBERTS, a citizen of the United States, and

a resident of Cincinnati, county of Hamil-' cylinder embodying my invention constitutes an engine of the two-cycle type, in which pistons stroke.

an explosionftakes place at one end of the One object of my invention is to provide a hand tool, of the impact type, with simple and effective means for imparting a blow to a drill bit, chisel, or the likesuch means,

in the form of a relatively free piston. or I plunger, being. driven by an explosive force. A further object of my invention is to provide means for returning the blow-imparting piston or plunger after it hasdelivered the blow and for this'purpose I have arranged rotative camming means that will impart return movement to said piston or plunger simultaneously with such rotative movement.

A further object of my invention is to .provide a rotor arranged to rotate on the axis of the blow-imparting member; said I rotor comprising a fly-wheel and the camming means whereb saidblow imparting member is retracte on the non-explosive stroke.

A further object of my invention is to arrange the fly-wheel so that its rotative movement will effect cooling of the cylinder; the fiy-wheel having its spokes setat an angle in the form of fan blades so as to draw a strong current f air over the outer wall of the cylinder.

And a still further object of my invention is to arrange the necessary details of construction whereby the reciprocative movements of the piston and the rotative movementsof the camming means will be effected in proper order.

These and other features of my invention are more fully described hereinafterf referencebeing had to theaccompanying drawings, in which:

Figure 1, is a sectional elevation of one form ofimpact tool embodying my invention; taken on the line I.I, Fig. 2.

Fig. 2, is a view in elevation of my improved impact tool, partly in section'on the line II.-'II, Fig. 1.

' igs. 3,) 4.- and 5, are diagrammatic views, showing the piston and camming means which I employ to move the piston in one direction, in several positions assumed during the operation of the tool.

Fig. 6,'is a side View, partly in section,

of the H -wheel, and

Figs.

and 8, are cross sectional views on the lines VIIVII and VIII-VIIL Fig. 1.

In Figure 1, which shows a longitudinal section of my improved im act tool, the

cylinder is indicated general y at' 1. This" cylinder may be in one piece, with a handle 2 at one end of the s'ame and, if desired, this handle may be a separate piece properly attached to the cyllnder. The bore of the cylinder may .be of uniform diameterthroughout its length, and it may be counthe cylinder heads 3 and-4, hereinafter described.

The piston is indicated at 5, and may be made of any suitable metal, cylindrical in contour, bored longitudinally at 6, for the passage of an explosive mixture and bored transversely to receive a cross-head 7, which ma be tapered, the ends of the .terbored and tapped at each end to receive same projecting beyond the surface of the piston, as indicated at\7 In addition this cross-head may be bored at 7 in hne with the bore 6 of the piston, "to provide an uninterrupted passage for the explosive mixture.

Surrounding the cylinder is the rotor whichincludes a fly-wheel 8, having a hubv :9, mounted on suitable anti-friction bearings, which may comprise cones 1O andlO" carried by said hub, and cones 11 and 12 carried by the cylinder 1, with interposed balls13; the gone 12 being threaded on the cylinder and maintained in the desired po-' sition by a locking rin I4. Attached to the' interior of the fly-w eel hub 9, in any suitable manner, or formingpart of the latter, are a air of cam members, 15 and 16, between w 'ch is formed a cam groove 17,

' cylinder and into the groove 17 formed bewith which theprojecting ends 7 of the cross-head 7 cooperate; said cam members being more clearly-shown in Fig. 2, andm the diagrammatic views, Figs. 3, 4 and 5 I .The handle end of the cylinder receives the head 3 which may be. held in place by a hollow screw 18, and packed by means of -a asket l9. Theupper end of the piston 5 1s threaded to receive a valve cage 20,

tween the cam members and 16, for the purpose of imparting motion to said cam members and through the latter to the flywheel 8, ,during the forward movement of' the piston, due to theforce of the explosion, and for the added purpose of impart ing return motion to the piston due to the kinetic energy stored in the fly-wheel, as

' hereinafter described.

The opposite end of the cylinder'receives the head4', whidh may be screwed tightly into place, and this head may be bored to closely fit the end of a tool or drill shank 25, which may be held to the head by a spring yoke 26; the latter engaging pins 27 carried by the head 4. A spring 28 may be interposed between the head 4 and a shoulder29, carried by the tool shank, and the pressure exerted against said shoulder 29 by the spring 28 will normally force this shoulder against the yoke 26.

, In the position referred to, that is with the shoulder 29 held by the spring 28 against the yoke 26, the inner end of the tool or drill shank will be' flush With the inner end of the head 4, and beyond the end of the piston when the latter is at the extreme end of its power stroke. .When pressure is exerted by the operator pressin the tool.

against its work, however, such too is forced inward against the spring 28 until it as sumes the position shown in Big. 1, with the shoulder 29, in contact with theouter end of the head 4. When in this position,

.the inner end of the tool will be in position to .be struck by thepiston at the end of its power stroke, as hereinafter described. The operator may, by var ing. the pressure of the tool against its work vary the extent to which the tool is forced into the cylinder, and thus control the force of the blow struck by the piston. In other words, the greater the pressure brou ht to'bear upon the tool, the more powerful will be the blow struck by the piston.

The outer wall of the. cylinder, immediately surrounding the combustion chamber,

is grooved at 30, providing ribs 31, forair cooling. Surrounding these ribs and the hub of the fly-wheel and having cured by any suitable fastening means. Onv

the opposite side offthe fly-wheel I may also place a protective member of reticulated or foraminous material; perforated metal, for

instance, as indicated at 3 4, which may be heldiin place by fastening means such as indicated at 35. Openings 36 may be pro-- vided in the head 3- to permit air to be drawn vtherethrough for cooling. the same and a spark plug 37, carried thereby. Air

is drawn through these openings'36, and

through the. passages formed by the grooves 30 between the ribs 31 and the hood, by means of bladed spokes 8 carried by the A mixing valve is indicated at 38, and while this arrangement is entirely practicable for use with my improved impact tool, it is obvious that any suitable form of car-- bureting device may be employed in lieu thereof, hence -I do not wish to confine myself to any particular form of fuel feeding or mixing device. I have shown the handle as provided with a lever 39 for controlling a throttle valve .40; said lever beingv connected with the valve by means of a controlling wire 41, which may lie in a groove 42, formed in the outer-wall of-the cylinder.

I may providemy improved impact tool with a timing device for the'sparking operation, comprising an insulated'ring 43, of fibre or" other suitable material, carried by a pair of metal contacts 44; the cylinder being provided with an insulated ring 45, of fibre or other suitable material, having'a spring-controlled member 46, for engagement with said metal contacts.

In the operation of my improved impact tool, the explosive mixture is drawn from the mixing valve 38 (when used), on the return stroke of-the piston. On the power stroke of the piston, the mixing valve 38 is closed, and the mixture may be compressed to a pressure of approximately ten pounds per square inch. .Just before the completion of this stroke, the piston uncovers exhaust ports 47, and the spent gases from the previous explosion escape to the atmosphere. As soon as the pressure in the space between the piston and the head 3 falls below that in the portion of the cylinder at the opposite end of .the piston, the valve 21 will be opened, admitting a fresh charge through said valve. to the explosion or working end of the cylinder. On the return stroke of the piston, the valve 21 closes,..the mixture is compressed and subsequently'igthe ensuing explosion nnparts the power stroke to the piston, completing the cycle of operations, which is repeated thereafter.

It should be noted that four complete strokes, or two power and two return strokes, are made by the piston during each revolution of the fly-wheel.

Motion during the'explosion or working stroke is transmitted to the fly-wheel 8, through the cross-head 7, (the ends of which are constrained by the slots 23 to move longitudinally of the cylinder), and the cam groove 17. On the completion of-the explosion stroke, the inertia of the'fiy-wheel maintains its rotation and causes it to impart motion through the cams and projecting ends of "the cross-head to return the piston.

I In Fig. 3, the piston is shown on its working stroke; moving in the direction of the arrow a. During this stroke the projecting end 7 is being forced against the side of the cam 15 at the point as; turning the cam in the direction of the arrow 6, and thereby imparting a rotary motion to the flywheel 8,

to which said cams are attached.

In Fig. 4, the piston has approached the end of its outward or working stroke, (the position assumed, if the stroke were completed, being indicated by broken lines). The movement of the piston, however, has been arrested by coming in contact with the end ofthe tool 25, which it strikes for cibly. It will be noted that were thecam groove 17 at this point of just suflicient width to permit the passage of the projectving end 7 *i, the force of the blow would react upon the entire structure of the drill. In order to permit the shortening of the piston stroke without reaction upon the structure, the cam groove is made-wider at this point; the distance y between opposite sides of the groove being greater than the sum of the diameter of the projectingend and the distance w to which the stroke of the piston is shortened due-to striking the end of the tool 25. Hence, for reasons set forth, the piston is free of all restraint by'the cams at the moment of striking the tool.

It is recognized that there will be a certain amount of rebound to the piston at the moment of striking the tool, which would cause the projecting end to strike the upper side of the cam groove, were the cam 12 stationary at that moment. However, 0wing to the fact that the cam is turning rapidthe piston. During this stroke, after the ly, due to the inertia of the fiy-wheel, the

inertia due to the rebound of the piston from the tool hasbeen spent, the inertia of the flywheel causes the cam 15 to exert pressure against the side of the projecting end at the point 2. Since the projecting end is restrained in its motion rectilinearly, the pressure exerted by the cam forces the piston in the direction of the arrow 0 causing it to complete its compression stroke.

It will be recognized, of course, that so long as there is a continuous series of explosions, tendin to impart p wer strokes to the piston, t e projecting end 7 is in contact with the cam 15; the cam 16 being brought into contact with the projecting end only when the fiy-wheel is being turned by hand, preliminary to and during starting.

To recapitulate, the movement of the pis- .ton during the explosion stroke is shown in Fig. 3, with the piston imparting motion to the fiy-wheel 8 through the medium of the projecting end of the cross-head 7; pressing against the cam 15 at the point w. The position of the piston at the moment of striking the tool 25, is shown in Fig. 4, at which time the piston is free from all other restraint than that due to the tool itself. The return movement of the piston during the compression stroke is shown in Fig. 5, with the flywheel imparting movement, due to its kinetic energy, to the piston through the cam pressing'against the projecting end at the point z.

The construction of my improved impact tool is primarily that of a two-cycle explosion en ine, adapted to the purpose herein set fort In comparing it to an ordinary base-compression, two-cycle engine, it may be said that the space between the working end of the piston, the head 4, and the end of the tool 25, corresponds to the crank-case of the ordinary engine. The passage through.

the piston corresponds to the by-pass or transfer port; the explosion chamber being similar to that of an ordinary engine.

The advantages of my construction lie in its simplicity and in the fact that the gases passing through the centre of the piston assist in cooling the same, and that at the same time, it warms the explosive mixture. Another advantage is that the mixture enters the centre of the combustion chamber, while the exhaust passes from ports piercing the walls of the cylinder all around the same. A further advantage in this construction lies in the fact that the piston at the moment of striking the tool is free from restraint, and no springs or other cushioning devices are required and therefore the full force of the explosion, less the slight amountrequired to move the fly-wheel andto overcome'the friction of the piston against the cylinder walls, is exerted against the tool. In this manner, the action of this structure corresponds very closely to that of the ordinary air drill or riveting hammer. Great simplicity is secured because of the fact that the machine as arranged avoids theuse of a connecting rod and crank-shaft; the function ordinarily performed by these parts being taken care of by the cam members'carried by the-fly-wheel. I secure compactness in arranging the flywheel to surround the cylinder, and a further advantage lies in the avoidance of excessive weight by omitting theconnecting l rod and crank shaft.

A further advantage lies in the 'fact that the piston makes twocomplete cycles to one revolution of the fly-wheel, instead of two plug method of placing the tool in an operative position. is a perfectly natural one pressure being applied by the operator pressing the drillvagainst the work; Avstill further advantage lies in the fact that the'operator can control the force of the blow by varying pressure exerted against the 'tool.

No ignition system other than a spar is shown in the drawings, since it is obvious that various forms of ignitionv depiston by an explosive force-, a cross-head carried by said piston and-having an endprojecting through said slot beyond the vices may be employed, and I do not wish to= limit myself to the use of any, particular form. y a

.Icl aim:' "i f i 1. The combination .in an impact tool, of a cylinder having a longitudinal slot there through, a tool-bit operatively connected to, one end of said cylinder, a piston longitudinallymovable therein and arranged to strike said tool-bit at one end of itsstroke, means for imparting striking movement to said outer'surface'of the cylinder, a cam rotatably-mounted with respect to said cylinder and encircling the same; said cam cooperating with the'projecting end of said cross-.

head, and a fly-wheel "operatively connected with said cam; said cam and cross-head be 1 ing arranged to convert the rectilineal movement of'said iston into rotary movement of said fly-whe -whereby the latter may re 'tract said piston after each power stroke.

"2. In a portable impact tool, the combination of a'cylinder having a longitudinal slot therein, a blow-imparting piston member therein, g v v mounted on said cylinder and encircling the a fly-wheel member rotatably same, an operative connection including a cam carried by one of said members and a cross-headcarried by the other of said members and extending through said slot whereby movement may be transmitted to said flywheel member from said piston member, and a tool yieldingly connected to said cylinder and successively struck by said piston-member at the ends of its power strokes, said fly-wheel member being operative to momentarily disengage said cam and said crosshead when the working stroke of said piston member is lesscthan a full stroke.

3. In a portable impact tool, the combination of a cylinder having a longitudinal slot therethrough, 'a blow-imparting piston therein, a fly-wheel rotatably mounted on said cylinder and encircling the same, an operative connection including a cam carried by the flyr-wheel and a cross-head carried by the piston and extending through said slot whereby motion may be transmitted to said.

fly-wheel from said piston, and a tool yieldingly (connected to said cylinder and successively) struck by said piston at the ends of its power strokes, said fiy-wheel being opera tive to momentarily disengage said cam and said cross-head when the working stroke of said piston is shortened by the impact there- 'of with said tool.

4. In; a portable impact tool of the explosive type, the combination of a cyllnder.

having a longitudinal slot therethrough, a

blow-imparting piston reciprocable in said cylinder, a fly-wheel encircling the cylinder, an operative connection between said piston" and said fly-wheel including a cam and a cross-head having .a projecting end extendin through said slot andbeyond said cylinder into engagement with said cam, and

a tool carried by said cylinder and arranged to be struck by said'piston at the end of the working stroke, said cam being momen- 'tarily carried by said fly-wheel out of'operative engagement with said cross-head when the forward stroke of the piston is shortened by the impact thereof with said tool.

5. In a portable impact tool a cylinder,

a blow-imparting piston reciprocable in said cylinder, a rotor surrounding said cylinder" and rotatable .with respect to the same, bearings for said rotor surrounding said cyhnder, a valve for admitting fuel to said cylinder, and a control wire for operating said der.

6. Thecombination, in'a portable impact tool, of a cylinder,- a tool-bit slidingly mounted in one end of said linder and projectingv into the chamber of he same, a

blow-imparting piston longitudinally movable insaid cylinder, provision for impart- 'in'gstriking movement to said piston by an explosive force whereby thepiston is brou ht a cross-head carried by said piston and having an end projecting through the wall of said cylinder and operative to prevent relative rotary movement between said piston into forcible engagement with said -toolit,

valve; said wire passing between said rotorq and its bearings and the wall of said cylinand cylinder, a cam surrounding said cylinder and cooperating with the projecting end of said cross-head and a fly-wheel encircling the cylinder and operatively connected with said cam; said cam and cross-head being arranged to convert the rectilineal movement of said piston into rotary movement with respect to the same, and cooperating I means carried by the piston and rotor for preventin relative rotary movement between sai piston and cylinder and for con verting the rectilineal movement of the PlS-r ton into rotary movement of the rotor, whereby the latter retracts said piston after each power stroke, said piston. being free to rebound slightly at the moment of impact out of engagement with said rotor.

8. In a portable impact tool, the combination of a. cylinder, a tool-bit yieldingly mounted in'the end 'of said cylinder, a blowimparting piston longitudinally movable in said cylinder, provision for forcibly moving said piston in one direction by an explosive force, a cross-head carried by said piston and having an end projecting through the wall of the cylinder, a rotor surrounding said cylinder and provided with a cam for cooperation with the projecting end of said cross-head, said cam and cross-head being arranged-to convert the rectilineal movement of said piston into rotary movement of said rotor and the rotary movement of the latter into rectilineal movement of the piston after the piston has engaged the tool-bit, said cam being so designed as to permit rebound of the piston without interference of the cam with said cross-head.

9. In a portable impact tool, the combination of a cylinder having a bore therethrough, a piston reciprocable therein, a hammer-head unitary with said piston and slidingly fitting the bore of said cylinder, a tool-bit mounted in one end of said cylinder-for engagement by said hammer-head, a

fly-wheel surrounding said cylinder and rotating with'respect to said cylinder, and cooperating means including a cross-head carcross-head travels an ried by said piston, a cam carried by said fly-wheel and engaged by said cross-head, and a guide in said c linder in which said operative to prevent relative rotation of said piston with respect to said cylinder, said cooperating means being operative to convert rectilinear movement of said piston into rotary movement of said fly-Wheel and vice-versa, said-piston be ing impelled by an explosive force at an undim'inished speed up to the moment of its impact with said tool-bit and being free to rebound and momentarily break the engagement of said cam and said cross-head at the moment of impact.

10. In a portable impact tool, the combination of a cylinder, a tool-bit slidingly mounted in one end of said cylinder, a blowimparting piston longitudinally reciprocable in said cylinder, a cross-head carried by said piston, the walls of said cylinder being longitudinally slotted to guide the projecting end of said cross-head and "to prevent relative rotation. of said piston, a cam surrounding said cylinder for cooperation with the projecting end of said cross-head, means for impelling, byan explosive force, said piston into engagement with said toolsbit, and a fly-wheel operatively connected with said cam, said parts being arranged to convert the rectilineal -movement of said piston into rotary movement of'said fly-wheel and the rotary movement of the latter into rectilineal movement of the piston'after the engagement of the piston with the toolbit, said piston being out of engagement with said cam and moving with undiminished speed at the moment of impact.

11. In a portable impact tool, the combination of a cylinder, a tool-bit detachably and yieldingly 'inountedin one end of the same, a blow-imparting piston member re ciprocable in said cylinder for impact against said tool-bit, said piston member and cylinder being restrained from relative rotary movement with respect to each other, a rotor member mounted to rotate onan axis substantially coincident with the axis of said cylinder, a cam carried by one of said members concentrically with the axis of said cylinder and a cross-head carried by the other of said members and cooperating with said cam, whereby the movement of one member is imparted to the other; the piston I,

being retracted by said rotor member, said,

piston member being momentarily out of engagement with and clear of said rotor member at the moment of impact.

12. In an impact tool, the combination of a cylinder, a piston operating within said cylinder to compress an explosive mixture during the working stroke and to transfer the same to the head end of the cylinder at the end of the said working stroke on the principle of a single acting two-cycle explosive engine,a hammer rigid with said piston and moving as one therewith, a balance wheel, a cam rigidly connected to said wheel and co-incident with the longitudinal axis of said cylinder andimpact receiving means stru'ck" by said hammer immediately prior to the end of each working stroke of said piston, said piston throughout its working stroke up to the moment of its impact against said impact receiving means being moved or impelled byan explosive. force at a substantially constant linear speed and being in driving engagement with said cam to impart a substantially constant speed of rotation to said wheel, the momentum of said wheel being operative to momentarily move said cam out of-engagement with said 15 a piston at thesaid moment of impact and to then bring said cam into re-engagement with said piston to return said piston to the rearward limit of its compression stroke. v

In witness whereof I have signed this 20 specification. 1

EDMUND WILLSON ROBERTS. 

